The present invention relates to an electrically conducting polymer composition or ohmic contact-providing composition comprised of a fluorinated carbon filled fluoropolymer. The ohmic contact is useful as a coating for hole transport layers, and especially, for aromatic amine hole transport layers, reference for example U.S. Pat. No. 4,265,990. In an embodiment, the ohmic contact-providing composition is coated onto a hole transport layer, thereby forming a perfect hole injecting or ohmic contact to that layer. As an alternative embodiment, the ohmic contact-providing composition can be coated onto a supporting substrate, and a transport layer can be coated on the composition. The composition can be selected as an injecting or ohmic contact for holes into materials which are capable of transporting electronic charge. The composition may be useful in any active organic device that depends for its operation on contact to an external circuit where the contact interface does not itself inhibit the supply of charge. The polymer composition ohmic systems, when coated or otherwise deposited onto a hole transporting layer yield the ohmic interface useful for optimum device performance. Further, the polymer compositions of the present invention, in embodiments, will retain ohmic contact with the same transport polymers even after the transport molecules or transport polymers have been rendered conductive by chemical modification. The compositions of the present invention are particularly useful for organic light emitting diode structures, field effect transistors, and any other active organic device that is capable of carrying an electrical current.
Substantial research has been conducted on finding compositions which form ohmic contact layers to media which efficiently transport charge. In general, it is difficult to make stable ohmic contact to organic insulators and semiconductors. Problems encountered in providing an ohmic contact to organic media arise from intrinsic effects like interfacial energy mismatch as well as incompatibilities between the contacting surfaces associated with extrinsic factors like chemical contaminants. When there is such an energy mismatch or electrical incompatibility, the result is a decrease in the efficiency of the interfacial transfer of charge. In these so-called emission limited situations, the contact controls the supply of current which can limit device performance. Therefore, the desired situation is to have a perfect ohmic contact between the current source and the device to which the current is provided in order to obtain a 100% efficient current flow. In the latter case where the contact does not limit the supply of charge carriers to the bulk of the transport medium, the current is said to be bulk controlled.
The compositions of present invention have solved or minimized the above problems by providing an organic composition which, when coated onto or otherwise applied to a transport medium, supplies fully as much charge as the bulk of the transport medium can accommodate under the action of an applied electric field. In embodiments, the supply of electrical current is, therefore, not limited by the contact layer.